The Altar That Must Not Be Touched by Iron

Near the end of the revelation at Sinai, tucked after the Ten Commandments and before the laws of slavery and damages, comes a commandment so strange it has puzzled readers for centuries. God forbids Israel from using iron tools to build the altar. “For if thou lift up thy tool upon it, thou hast profaned it” (Exodus 20:22). Why should the altar care about how it was shaped? A stone is a stone.

Midrash Tanchuma, Yitro 17, compiled in the fifth and sixth centuries CE, gives the answer through a logical argument that then expands into something far larger than a rule about construction. Since the altar was created to prolong human life, and the iron sword was made to shorten it, it would not be fitting to use a life-shortening tool on a life-prolonging structure. That is the practical logic.

But then Rabbi Johanan the son of Zakkai, the great sage who survived the destruction of the Temple and rebuilt Jewish life at Yavneh after 70 CE, pushes the argument into new territory. He quotes (Deuteronomy 27:6): “Thou shalt build the altar of the Lord thy God of unhewn stones, for it will help to achieve peace between the Israelites and their Father in heaven.” Then he runs a logical inference in the other direction: if the stones of the altar, which cannot see or hear or speak, achieve peace between Israel and God, and therefore the Torah protects them from the degradation of iron, how much more should we protect the one who promotes peace between a husband and wife, between a man and his companion.

The Tanchuma draws one more step from the original prohibition. The verse reads: “Neither shalt thou go up by steps unto mine altar, that thy nakedness be not uncovered thereon” (Exodus 20:23). From this the rabbis derived a principle about human dignity that has nothing to do with altars at all. If God is careful not to shame a stone, which understands neither good nor evil, how much more careful should we be not to shame a companion, who is formed in the likeness of God Himself.

The stone cannot be embarrassed. It has no feelings to hurt. And yet God, in designing the ritual architecture of the covenant, built in a protection for it anyway. The rabbis are saying: look at what the Holy One considers worth protecting. Then recalibrate accordingly when you are dealing with a person made in the divine image.

This is the Tanchuma at its most characteristic. It begins with a specific ritual law, narrow and technical, and it opens outward until it has said something about what it means to be human and how to treat other humans. The logic of the altar teaches the logic of the community. The prohibition against iron tools becomes a teaching about peacemakers. The ban on steps becomes a teaching about dignity.

The text closes with a quiet comment on the evil inclination, the yetzer hara (יצר הרע). Because of it, the Tanchuma says, one’s years are shortened in this world. But in the world to come, “He will swallow up death forever; and the Lord God will wipe away tears from all faces” (Isaiah 25:8). The stone altar, immune to temptation, is treated with care. The human being, who has a yetzer hara pulling at them every day, is treated with even more. That is the logic of the Tanchuma’s final move: the very weakness that makes us capable of sin is precisely what makes our dignity worth guarding.

The peacemaker’s life is prolonged. The one who promotes harmony between husband and wife, between neighbor and neighbor, inherits the quality of the unhewn stones of the altar, which asked nothing and were honored anyway. The tradition does not forget either of them.